Lung Cancer Overview

Lung cancer is the leading cause of cancer deaths in women and men both in the United States and throughout the world. Lung cancer has surpassed breast cancer as the leading cause of cancer deaths in women. In the United States in 2010, 157,300 people were projected to die from lung cancer, which is more than the number of deaths from
colon and
rectal, breast, and prostate cancer combined. Only about 2% of those diagnosed with lung cancer that has spread to other areas of the body are alive five years after the diagnosis, although the survival rates for lung cancers diagnosed at the earliest stage are higher, with approximately 49% surviving for five years or longer.

Cancer occurs when normal cells undergo a transformation that causes them to grow and multiply without control. The cells form a mass or tumor that differs from the surrounding tissues from which it arises. Tumors are dangerous because they take oxygen, nutrients, and space from healthy cells and because they invade and destroy or reduce the ability of normal tissues to function.

Most lung tumors are malignant. This means that they invade and destroy the healthy tissues around them and can spread throughout the body.

The tumors can spread to nearby lymph nodes or
through the bloodstream to other organs. This process is called metastasis.

When lung cancer metastasizes, the tumor in the lung
is called the primary tumor, and the tumors in other parts of the body are called secondary tumors or metastatic tumors.

Some tumors in the lung are metastatic from cancers elsewhere
in the body. The lungs are a common site for metastasis. If this is the case,
the cancer is not considered to be lung cancer. For example, if prostate cancer spreads via the bloodstream to the lungs, it is metastatic prostate cancer (a secondary cancer) in the lung and is not called lung cancer.

Lung cancer comprises a group of different types of tumors. Lung cancers usually are divided into two main groups that account for about 95% of all cases.

The division into groups is based on the type of
cells that make up the cancer.

The two main types of lung cancer are characterized
by the cell size of the tumor when viewed under the microscope. They are called small cell lung cancer
(SCLC) and non-small cell lung cancer (NSCLC). NSCLC includes several subtypes of tumors.

SCLCs are less common, but they grow more quickly and are more likely to metastasize than
NSCLCs. Often, SCLCs have already spread to other parts of the body when the
cancer is diagnosed.

About 5% of lung cancers are of rare cell types, including carcinoid tumor,
lymphoma, and others.

The specific types of primary lung cancers are as follows:

Adenocarcinoma (an NSCLC) is the most common type of lung cancer, making up 30% to 40% of all cases. A subtype of adenocarcinoma is called bronchoalveolar cell carcinoma, which creates a pneumonia-like
appearance on chest X-rays.

Squamous cell carcinoma (an NSCLC) is the second most common type of lung cancer, making
up about 30% of all cases.